Signaling arrangement for two party telephone lines



May 31, 1932. vW H EDWARDS 1,860,459

SIGNALING ARRANGEMENT FOR TWO-PARTY TELEPHONE LINES Filed June 27, 1931 nected thereto, such for example as two party V'line' to tell whichstation is calling so .that

iPatented May 31, 19,3217 s Y i UNITED :stares il 1860,459i

PATENT* Porri-cia?" 5 WILLIAM HorrLE EDWARDS, or GREAT NECK, NEWYORK,v ASSIGNOR fro AMERICAN TELEPHONE `Alvi) TELEGRAPH COMPANY, A CORPORATION or NEW YYoan SIGNALING ARRANGEMENT non Two PARTY 'rELEPHoNE'LINEs Application filed June 27,

This invention relates to telephone systems and more particularly to improvements in signaling or ringing arrangements associated with the'lines of such systems. v

The ringing circuit arrangements of the invention are. particularly adapted for telephone lines having a plurality of stations condial message rate lines-, .When the ,telephone line serves two subscribers stations'with'message ratev service7 er in other words when each station i is charged Vseparately for the number-of calls therefrom7` certain apparatus is provi ded at the central oiiice for making identification tests when a call comes in from the the'properA station may be charged with the call. The central otlice equipment for malringthis identiiication test7 whereby' the proper station may be charged for the outgoing call, is so designed as to require for. its operation thepresence of a 1000 ohm dri-c resistance ground at the station'when the tip partyis calling and the absence of this ground when the vring yparty is calling. It has been the practice to provide this 1000 ohm ground throughI the ringer apparatus at the station when the tip '.party; is calling. In other words a 1000 ohm d-c resistance ringer which isapproximately 22,000 ohms imped-k ance at 500 cycles would be connected to the ltip side of the line and a. similar ringer` would be connected tothe ring side of the line. A

vcondition wherein a ringer of low impedancek is connected to one Vside of the line and there is no party connected to the other sideof the line results in an unbalanced condition which i mightibe quite undesirable when ythe line has inductive exposures which in lturn would cause the induced currents to flow through the i' induction Acoil at the subscribers station and cause noise in the'receiver thereat.A A

similar unbalance is present when twoor more ringers are connected to one side of the line and a different number connected to the other side. f

Itis the primary objectief the invention to 1931'. serial No. 54:/,33a

Vbut l.will have its circuit connections so arf ranged thatno inductive interference or noise will result .in the receiver at the station.

Other-'objects and features of the 'invention will appear more fully from the detailed deyscrlption thereof hereinafter given. f, :The invention may be more fully undertof stood from the following ydescription together with the accompanying drawings iny theV Figures l, 2 and 3 of which the invention is illustratedj Fig. l is a circuit diagram embodying a preferred form of the invention.

lTigsQv and 3 are schematic diagrams illus- Y trating the principles ofoperation of theinventlon.` 'Similar reference characters have been used to denote like parts in Figs. 2 and 3.

'HiA

AIn Fig. l is shown a telephone line to which would be connected ythe subscribers y stations l0 and l1. The line L illustrates a twopartydial message rate circuit. At the central oce the line would be associated with `line iindler apparatus 2.and selector apparatus l. As'such apparatus is well known in the lart no `further description thereotwillbe inthe'dialing operationA a ground will monientarily beapplied to conductor 3 and relay 4 will lle/operated.y This will connect the tip and ring sides of the line-to (conductor 6 which is connected `to the marginal relay 7. The function of relay 7 is to control a circuit 8 leading to register apparatus 9.2 The relays 4 and 7 and the appartus c assciated therewith are utilized to make an, identificationtestso that theQproper stationmay be` charged for outgoing calls on ,a line of this type. As vhas heretofore beenpointed out Athe identification-test, or operation of marginal relay 7, depends onvthe presenceof a a5 given except that at'the end of the first digit c 1000 ohm ground at the station when the tip party is calling and the absence of this re atively low d-c resistance ground when the ring party is calling. In other words the marginal relay will operate when the tip party is calling but will not operate when the ring party is calling. In this mannerthe proper one of the calling part-ies may be identified and the call charged thereto.

As has been pointed out the presence of a 1000 ohm d-c resistance ground connected to one side of the line through the ringer, or in other words the connection of a relatively low im edance ringer to the line and ground, might e quite undesirable because of the susceptiveness of stationV sets with such ringers to inductive noise and because the low impedance ringers are less satisfactory fronra ringing standpoint. This susceptiveness will appear more readily from Figs. 2 and 3. When the line L has inductivey exposures longitudinal currents might be set up in the tip and ring sides of the line. If a low impedance ringer 23, such as the 1000 ohm d--c resistance type with the impedance of 22,000 ohms at 500 cycles, is connected to the tip and there is no party connected to the yring side of the line,.as shown in Fig. 2, the

induced currents would follow the direction shown by the arrows. The two sides of the line would not be balanced and currents would flow through the'induction coil 24 to ground through the low impedance 23. This would cause noise in the receiver R. If, as shown in Fig, both ringers connected to the tip and rin are of yrelatively high impedance as 22 an 25, namely 110,000 ohms at 500 cycles or if a ringer with a low impedance winding as 26 is connected to the mid oint of the induction coil winding then Lthe induced currents as shown by the arrows will have no effect on the secondary of the induction coil 24 and will not affect the receiver R. Likewise, if the ring party is not connected, and the impedance 22 is not present the slightly unbalanced condition created will have a 'negligible effect from a noise standpoint. The arrangements of the invention present the advantages shown schematically in Fig.`3. In other words when the rin party is calling the ringers are both of hi impedance, but when the tip party is ca ling the ringer is changed so that while its d-c resistance is only 1000 ohms, its 500 cycle impedance is 18,000 ohms and furthermore it is connected, to the midpoint of the subseribers induction coil so that the receiver will not be affected by noise.

In Fig. 1 is shown in more detail the station ringing apparatus of the invention for obtainingthe advantages of high impedance ringers atfthe stations, and also for meeting the requirement of the identification test circuit for a 1000 ohm ground when the tip party is calling.y The ring party is shown as station 11. This station includes the usual induction coil 18, receiver 19, transmitter 20, dial 27, and switch hook contacts 28. Connected to the ring side of the line and ground is the high impedance ringer 21 having an impedance of approximately 4300 ohms for purposes of illustrating the invention. The tip party is shown as station 10. This station includes the induction coil having windings 12 and 15, the receiver 13, the transmitter 14, 'dial 29 and s'witch'hook contacts 30. The ringer 16 is provided connected through condenser 17 to the tip side yof the line. The ringer 16 has a lower right hand winding of approximately 1000 ohms, which together With its other windings, is equal in voice frequency and ringing frequency impedance to the regular high impedance ringer used for the ring party at station 11. The switch contacts 30 of station 10 are so arranged that, when the tip party at station 10 is not tall;- ing, the rin er 16 is connected in the same manner astie ringer 21 at station 11, or as a high impedance ringer, thus providing a circuit of rlow susceptiveness to inductive noise currents. When the tip party :it station 10 is talking the lower right hand winding of ohms of ringer 16 is connected in the station set at a point such as 50 between the windings 12 and 15 of the inductiony coil which is substantially balanced with respect to the tip and ring of the line. With the above arrangements the receivers will not be subjected to inductive noise and the requirement of the 1000 ohm ground for the identification test will be met.

While the invention'has been disclosed as embodied in certain specific arrangements which are deemed desirable it is understood that it is capable of embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.y

What is `claimed is:

1. A telephone line having two subscribers stations connected thereto, grounded ringing apparatus of high impedance connectedfto one side of the line at one of said stations, grounded ringing apparatus of high impedance connected to the other side of the line y at the other of said stations, and means at said last mentioned station operative when a call is initiated therefrom vfor reducing the impedance of the ringer thereat and for so changing its connection to theline that in- -ductive interference will not be ,caused by such connection.

2.l A telephone line having two subscribers stations connected thereto, groundedringing apparatus of high impedance connected to one side of the line at one of said stations, grounded ringing apparatus ofY high impedanceconnected to the other side ofthe line at the other of said stations, and means at said last mentioned station operative when va call is initiated therefrom for reducing the impedanceof the ringer thereat. and for cone necting the ringer to the line at a point in said station set which is substantially halanced with respect to the tip and ring sides y of said line. l

3. A telephone line having two subscribers stations connected thereto, grounded ringing apparatus of high impedance connected to onevside of the line at one of said stations5 i grounded ringing apparatus of high impedance connected Ato the other side of the line at the other of said stations, and means at said last mentioned station operative when a call is initiated therefrom for reducing the impedance of the ringer thereat and for connecting the ringer to themid or neutral point of the subscribers inductionvcoil at said station.

4. A telephone line of theY two party dial kmessage rate type connecting two subscribers stations with a central olice,vma-rginal identiiication apparatus at the central oliice operative when aV lowy impedance ground is connected to the line when. one party is callingy andnon-operative'wh'en said low impedance ground is not connected to the line as when the second party is calling, grounded ringing apparatus of high impedance Vconnected to the ring side of the line -at the station of said iirst mentioned partly, grounded ringingapparatus of high impedance connected to the tip side of the line at the station of said first .mentioned party, and means operative when said first party calls for reducing the impedance of the grounded ringer thereat and for changing its connection so that the Sides kof the line will remain substantially balanced.

In testimony whereof, I have signed my name vto this specicationthis 26th day of June, 1931. Y f c WILLIAM I-LEDWARDS. 

